PUTRAJAYA, Malaysia (Reuters) - Malaysian opposition leader Mahathir Mohamad challenged the government to charge him under an anti-fake news law, after authorities said they were investigating him for false claims that his plane was sabotaged ahead of the general election.

FILE PHOTO: Former Malaysian Prime Minister and candidate for opposition Alliance Of Hope, Mahathir Mohamad, waves to his supporters during an election campaign rally in Kuala Lumpur, Malaysia May 3, 2018. REUTERS/Stringer/File Photo

Malaysia is in the middle of intense campaigning for an election on May 9 that pits Prime Minister Najib Razak against 92-year-old former premier Mahathir.

Critics say the new fake news law is aimed at curbing free speech and criticism of Najib, who is grappling with a multi-billion-dollar scandal at state fund 1Malaysia Development Berhad (1MDB), and popular anger over rising living costs.

“I’m going to be charged under the new fake news law... Go ahead and charge me,” Mahathir said at an opposition rally in the administrative capital of Putrajaya on Thursday.

“On May 9, we will take down this kleptocratic government led by one who is named Najib Razak,” he told thousands of cheering supporters.

Mahathir said last week that he suspected sabotage of a private plane that was to fly him from Kuala Lumpur to Langkawi, where he was to file his candidacy, after the pilot discovered some damage to the aircraft just before take-off.

The government ordered an investigation, following which the Civil Aviation Authority said the inquiry found no indication of sabotage. Its chairman said it was wrong to make such “wild and false” claims for political gain.

Malaysia’s inspector-general of police, Mohamad Fuzi Harun, told reporters police may call Mahathir in to give a statement in connection with the fake news probe “if there’s a need”.

Malaysia is among the first few countries to legislate policing of fake news. A Danish national was prosecuted last week under the law for inaccurate criticism of police on social media.

Mahathir and Najib have been targeting each other’s vote base in a fierce campaign. Najib is expected to retain power, but analysts are predicting a close contest.

Najib, who chaired 1MDB’s advisory board, has consistently denied any wrongdoing over the billions of dollars that were allegedly siphoned off from the state fund. A Department of Justice investigation is under way into 1MDB in the United States, along with probes in other countries, including Singapore and Switzerland.

At a campaign stop on Friday, Najib urged voters to look past the lies and slander thrown at his ruling coalition and choose the side that offers “the best agenda” for the country.

“Even as we are lashed by the tsunami of slander belittling the government and leaders, I would like to say that we cannot build a future for a nation-state based on slander and personal attacks,” he was quoted as saying in a report by state newswire Bernama.

The opposition has claimed the election will be unfair - a plan to redraw electoral boundaries was rushed through parliament just days before Najib called for polls.

Six opposition candidates were barred from contesting for either submitting incomplete documents or due to previous convictions or for being bankrupt.

Electoral watchdogs also said there were alarming discrepancies in the voting list that could bring into question the legitimacy of the whole process.